WO2022133960A1 - 电池组、电池包、电学装置以及电池组的制造方法及制造设备 - Google Patents
电池组、电池包、电学装置以及电池组的制造方法及制造设备 Download PDFInfo
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- WO2022133960A1 WO2022133960A1 PCT/CN2020/139181 CN2020139181W WO2022133960A1 WO 2022133960 A1 WO2022133960 A1 WO 2022133960A1 CN 2020139181 W CN2020139181 W CN 2020139181W WO 2022133960 A1 WO2022133960 A1 WO 2022133960A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
- H01M50/267—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders having means for adapting to batteries or cells of different types or different sizes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/04—Construction or manufacture in general
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
- H01M50/204—Racks, modules or packs for multiple batteries or multiple cells
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
- H01M50/204—Racks, modules or packs for multiple batteries or multiple cells
- H01M50/207—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape
- H01M50/209—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape adapted for prismatic or rectangular cells
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
- H01M50/244—Secondary casings; Racks; Suspension devices; Carrying devices; Holders characterised by their mounting method
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/50—Current conducting connections for cells or batteries
- H01M50/502—Interconnectors for connecting terminals of adjacent batteries; Interconnectors for connecting cells outside a battery casing
- H01M50/509—Interconnectors for connecting terminals of adjacent batteries; Interconnectors for connecting cells outside a battery casing characterised by the type of connection, e.g. mixed connections
- H01M50/51—Connection only in series
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2220/00—Batteries for particular applications
- H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- the present application relates to the technical field of energy storage devices, and in particular, to a battery pack, a battery pack, an electrical device, a method for manufacturing a battery pack, and a manufacturing device for a battery pack.
- Secondary batteries have the advantages of small size, high energy density, high power density, many cycles of use and long storage time, and are widely used in some electronic equipment, electric vehicles, electric toys and electric equipment, such as mobile phones, notebook computers, Battery cars, electric cars, electric planes, electric ships, electric toy cars, electric toy ships, electric toy planes and electric tools, etc.
- Secondary batteries are used as power drive power sources for new energy vehicles or large-capacity storage units in energy storage power stations. Multiple cells need to be connected in series/parallel to obtain battery packs, battery packs, or system electrical cabinets. In order to improve the safety of secondary batteries, a technical solution is proposed to connect a plurality of cells of different chemical systems to form a battery pack.
- One type of cells is, for example, lithium-containing nickel-cobalt-manganese with high energy density.
- a ternary battery of lithium metal oxide, another type of battery is, for example, a lithium iron phosphate battery with high safety.
- the present application is made in view of the above problems existing in the prior art, and its purpose is to provide a battery pack, which can ensure the energy of the cells with different charging and discharging characteristics by matching and designing the parameters of different types of cells. Quick charge and discharge are carried out uniformly, and safety problems such as lithium precipitation are not easy to occur during the fast charge process.
- a first aspect of the present application provides a battery pack, the battery pack includes at least a first type of battery cell and a second type of battery cell that are electrically connected in series, wherein the first type of battery cell and the second type of battery cell are Batteries of different chemical systems, the first type of batteries includes N first batteries, the second type of batteries includes M second batteries, and N and M are positive integers; the first batteries It includes a first negative pole piece, the second battery core includes a second negative pole piece, and the electrolyte conductivity (25°C) of the first battery core is the difference between the coating quality per unit area of the first negative pole piece.
- the ratio is denoted as M1
- the ratio of the electrolyte conductivity (25° C.) of the second cell to the coating mass per unit area of the second negative pole piece is denoted as M2
- the unit of the electrolyte conductivity is mS/cm
- the unit of the coating mass per unit area is mg/cm 2
- M1 and M2 satisfy: M1>M2, and 0.08 ⁇ M1 ⁇ 11, 0.03 ⁇ M2 ⁇ 4.62.
- the state of charge-open circuit voltage (SOC-OCV) curve of the first cell satisfies at least one of the following conditions: (1) In the SOC range of 5%-95%, the SOC of the first cell The slope k1 of the -OCV curve is less than or equal to 5mV/%SOC; (2) in the SOC-OCV curve of the first cell, there is at least a gentle curve with a span not lower than 10% SOC and a slope k1 ⁇ 5mV/%SOC.
- the state of charge-open circuit voltage (SOC-OCV) curve of the second cell satisfies at least one of the following conditions: (1) in the range of 5%-95% SOC, the second cell has The slope of the SOC-OCV curve k2>5mV/%SOC, optionally, k2 ⁇ 6mV/%SOC, further optionally, k2 ⁇ 9mV/%SOC; (2) SOC-OCV curve of the second cell Among them, there is at least a section of curve whose span is not less than 10% SOC and slope k2 > 5mV/% SOC.
- the compaction density of the first negative pole piece is PD1
- the compaction density of the second negative pole piece is PD2, where PD1 ⁇ PD2, and 0.5 ⁇ PD1 ⁇ 3, 0.5 ⁇ PD2 ⁇ 3 , the unit is g/cm 3 ; optionally, 1 ⁇ PD1 ⁇ 2, 1 ⁇ PD2 ⁇ 2; further optionally, 1.2 ⁇ PD1 ⁇ 1.7, 1.2 ⁇ PD2 ⁇ 1.7.
- the coating quality per unit area of the first negative pole piece is CW1
- the coating quality per unit area of the second negative pole piece is CW2, wherein 6.49 ⁇ CW1 ⁇ 17, 4.54 ⁇ CW2 ⁇ 25.51, The unit is: mg/cm 2 .
- the negative active material of the first negative pole piece and the negative active material of the second negative pole piece can be independently selected from artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials.
- artificial graphite natural graphite
- soft carbon soft carbon
- hard carbon hard carbon
- silicon-based materials silicon-based materials
- tin-based materials tin-based materials.
- materials and lithium titanate One or more of materials and lithium titanate.
- the ratio of the number N of the first battery cells to the number M of the second battery cells is 0.1-50, optionally 0.3-30, and further optionally 0.5-10.
- a second aspect of the present application provides a battery pack, which is characterized by comprising the battery pack described in the first aspect.
- a third aspect of the present application provides an electrical device, including the battery pack described in the first aspect above or the battery pack described in the second aspect above, and the battery pack or the battery pack can be used as the battery pack or the battery pack.
- a power source or energy storage unit for an electrical device including the battery pack described in the first aspect above or the battery pack described in the second aspect above, and the battery pack or the battery pack can be used as the battery pack or the battery pack.
- a fourth aspect of the present application provides a method for manufacturing a battery pack, comprising the steps of: obtaining a first-type battery cell and a second-type battery cell, wherein the first-type battery cell and the second-type battery cell are of different chemical systems batteries, the first type of batteries includes N first batteries, the second type of batteries includes M second batteries, N and M are positive integers, and the first batteries include a first negative electrode pole piece, the second battery core includes a second negative pole piece, and the ratio of the electrolyte conductivity (25°C) of the first battery core to the coating mass per unit area of the first negative pole piece is recorded as M1 , the ratio of the electrolyte conductivity (25° C.) of the second battery core to the coating mass per unit area of the second negative pole piece is denoted as M2, wherein the unit of the electrolyte conductivity is mS/cm, The unit of coating mass per unit area is mg/cm 2 , M1 and M2 satisfy: M1>M2, and 0.08 ⁇ M1 ⁇
- a fifth aspect of the present application provides a manufacturing equipment for a battery pack, comprising: a clamping arm unit, the clamping arm unit is used to obtain a first type of battery cell and a second type of battery cell, the first type of battery cell and the second type of battery cell
- the batteries are batteries of different chemical systems, the first type of batteries includes N first batteries, the second type of batteries includes M second batteries, N and M are positive integers, and the first type of batteries is a positive integer.
- a battery cell includes a first negative pole piece, the second battery core includes a second negative pole piece, and the electrolyte conductivity (25°C) of the first battery cell is proportional to the unit area of the first negative pole piece.
- the ratio of the cloth mass is denoted as M1
- the ratio of the electrolyte conductivity (25°C) of the second cell to the coating mass per unit area of the second negative pole piece is denoted as M2, wherein the electrolyte conductivity
- M1 and M2 satisfy: M1>M2, and 0.08 ⁇ M1 ⁇ 11, 0.03 ⁇ M2 ⁇ 4.62; assembly unit, the assembly a unit for electrically connecting the first type of batteries and the second type of batteries in at least series connection to form the battery pack described in the first aspect; and a control unit for controlling all the batteries the clamping arm unit and the assembling unit.
- the battery pack includes at least a first type of battery cell and a second type of battery cell of different chemical systems connected in series.
- the ratio of the coating mass per unit area of the sheet and the ratio of the electrolyte conductivity of the second type of cell to the ratio of the coating mass per unit area of the second negative pole piece are optimized to ensure that the first type of cell and the The lithium-evolution windows of the second type of cells are matched, so that the battery packs containing cells of different chemical systems can have good fast charging and discharging capabilities, and lithium precipitation is not easy to occur during the fast charging process.
- the battery pack and device of the present application include the battery module, and thus have at least the same technical advantages as the battery pack.
- FIG. 1 is a schematic diagram showing one example of a cell of the present application.
- FIG. 2 is an exploded view showing one example of the cell of the present application shown in FIG. 1 .
- FIG. 3 is a schematic diagram showing one example of the battery pack of the present application.
- FIG. 4 is a schematic diagram showing one example of the battery pack of the present application.
- FIG. 5 is an exploded view showing one example of the battery pack of the present application shown in FIG. 4 .
- FIG. 6 is a schematic diagram showing an example of a power consumption device using the battery pack of the present application as a power source.
- FIG. 7 is a schematic diagram showing an example of a charging curve when step charging of the first type of cells (lithium iron phosphate cells) in the battery pack is controlled by voltage according to an embodiment of the present application.
- FIG. 8 is a schematic diagram illustrating a charging curve when the step charging of the lithium iron phosphate cell is controlled according to the SOC value in the prior art.
- a “range” disclosed herein is defined in the form of a lower limit and an upper limit, a given range being defined by the selection of a lower limit and an upper limit, the selected lower limit and the upper limit defining the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive, and may be arbitrarily combined, ie, any lower limit may be combined with any upper limit to form a range. For example, if the ranges of 60-120 and 80-110 are listed for a particular parameter, it is to be understood that the ranges of 60-110 and 80-120 are also contemplated.
- the numerical range "a-b" represents an abbreviated representation of any combination of real numbers between a and b, where both a and b are real numbers.
- the numerical range "0-5" means that all real numbers between "0-5" have been listed in the text, and "0-5" is just an abbreviated representation of the combination of these numerical values.
- a parameter is expressed as an integer greater than or equal to 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.
- the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence.
- reference to the method may further include step (c), indicating that step (c) may be added to the method in any order, eg, the method may include steps (a), (b) and (c) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
- the "comprising” and “comprising” mentioned in this document indicate an open type, and can also be a closed type.
- the terms “comprising” and “comprising” can mean that other components not listed may also be included or included, or only the listed components may be included or included.
- the term "or” is inclusive.
- the phrase “A or B” means “A, B, or both A and B.” More specifically, the condition “A or B” is satisfied by either of the following: A is true (or present) and B is false (or absent); A is false (or absent) and B is true (or present) ; or both A and B are true (or present).
- secondary battery As the power drive power source of new energy vehicles or the large-capacity storage unit of energy storage power station, secondary battery needs to have high energy density, and people's requirements for the charging speed of secondary battery are also increasing.
- a step-type charging method is generally used at present.
- the charging curve of the above-mentioned stepped charging usually consists of multiple steps. In each step, the charging is continued at a constant current for a certain period of time, and then at the next critical point, the charging current increases, and the charging continues at a constant current in the next step.
- the stepped charging is generally regulated according to the lithium deposition window corresponding to the negative pole piece of the secondary battery (represented by the maximum charging current corresponding to the different SOC of the cell).
- the battery pack includes a plurality of cells with different chemical systems connected in series and charged with the same current, since the charge and discharge characteristics of the cells of different chemical systems are significantly different, how to realize the cells of different chemical systems It has become a technical problem to uniformly perform fast charging and discharging with high safety.
- cell refers to a battery cell that can be independently charged and discharged.
- the components of the battery cell may include positive pole pieces, negative pole pieces, separators, electrolytes, and outer packaging for encapsulating the positive pole pieces, negative pole pieces, separators, and electrolytes.
- the application does not have any special restrictions on the type and shape of the cells, which may be soft-wrapped cells, cylindrical cells, or square cells and other types of cells.
- the batteries in this application can be lithium-ion batteries, potassium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, etc., and are particularly preferably lithium-ion batteries.
- active ions are inserted and extracted back and forth between the positive electrode and the negative electrode.
- the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
- the "chemical system" of the battery cell is divided according to the composition of the positive electrode active material used in the positive electrode sheet in the battery cell, and the elements or substances that are doped or coated with the positive electrode active material are not limited.
- a battery cell whose positive active material is lithium iron phosphate (including doped with Mn or V element) can be defined as a lithium iron phosphate chemical system battery cell.
- a cell whose positive active material is nickel cobalt lithium manganate (generally referred to as NCM) can be defined as an NCM chemical system cell.
- the chemical system of the battery cell can be further limited according to the relative content of nickel , cobalt , and manganese elements in the positive electrode active material.
- the positive active material is LiNi 0.6 Co 0.2 Mn 0.2 O 2 (generally referred to as NCM622) battery can be defined as NCM622 chemical system battery, the positive active material is LiNi 0.8 Co 0.1 Mn 0.1 O 2 ( Generally referred to as NCM811) cells can be defined as NCM811 chemical system cells.
- the nickel-cobalt-aluminate lithium system battery (commonly referred to as NCA) as the positive electrode material can be defined as the NCA chemical system battery.
- NCA nickel-cobalt-aluminate lithium system battery
- a hybrid system cell can also be used, for example, a hybrid system cell including NCM and NCA.
- the battery cell of the present application includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, and the negative electrode film layer contains a negative electrode active material.
- the negative electrode active material in the negative electrode film layer can be a negative electrode active material commonly used in the art, for example, natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, One or more of lithium titanate.
- the silicon-based material may be selected from one or more of elemental silicon, silicon oxide, and silicon-carbon composite.
- the tin-based material can be selected from one or more of elemental tin, tin oxide compounds, and tin alloys.
- the negative electrode membrane in addition to the negative electrode active material, may further comprise an optional binder, an optional conductive agent and other optional auxiliary agents.
- the negative electrode membrane of the present application is usually formed by coating and drying the negative electrode slurry.
- the negative electrode slurry is usually formed by dispersing the negative electrode active material and optional conductive agent and binder in a solvent and stirring uniformly.
- the above solvent may be N-methylpyrrolidone (NMP) or deionized water.
- the conductive agent may include one or more of superconducting carbon, carbon black (eg, acetylene black, ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
- carbon black eg, acetylene black, ketjen black
- carbon dots carbon nanotubes, graphene, and carbon nanofibers.
- the binder may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA) , one or more of sodium alginate (SA) and carboxymethyl chitosan (CMCS).
- the binder may include one of styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS) or several.
- Other optional auxiliary agents are, for example, thickeners (such as sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials, and the like.
- the negative pole piece does not exclude other additional functional layers other than the negative electrode film layer.
- the negative electrode sheet of the present application may further include a conductive primer layer (eg, a conductive agent and a bonding agent) disposed on the surface of the negative electrode current collector sandwiched between the negative electrode current collector and the first negative electrode film layer. composition).
- the negative electrode sheet of the present application may further include a protective cover layer covering the surface of the second negative electrode film layer.
- the negative electrode current collector may be a metal foil or a composite current collector, for example, the metal foil may be a foil composed of copper foil, silver foil, iron foil, or an alloy of the above metals.
- the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. ) formed on the base layer of polymer materials (such as polypropylene PP, polyethylene terephthalate PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and its copolymers, etc.). formed on the base layer).
- polymer materials such as polypropylene PP, polyethylene terephthalate PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and its copolymers, etc.
- the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material.
- the positive electrode current collector has two opposite surfaces in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.
- the positive electrode current collector may be a metal foil or a composite current collector, for example, the metal foil may be an aluminum foil, and the composite current collector may include a polymer material base layer and a layer formed on the polymer material. A metal layer on at least one surface of the material base layer.
- the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) Glycol ester PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and its copolymers etc.
- metal materials aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.
- Glycol ester PET polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and its copolymers etc.
- the positive electrode active material can be a known positive electrode active material for battery cells in the art.
- the positive active material may include one or more of the following: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
- the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for battery cells can also be used. These positive electrode active materials may be used alone or in combination of two or more.
- lithium transition metal oxides may include but are not limited to lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811)), lithium nickel cobalt aluminum oxide (such as One or more of LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and its modified compounds.
- lithium cobalt oxides such as LiCoO 2
- lithium nickel oxides such as LiNi
- olivine-structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (eg, LiFePO 4 (LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (eg, LiMnPO 4 ), lithium manganese phosphate and carbon One or more of the composite materials, lithium iron manganese phosphate, lithium iron manganese phosphate and carbon composite materials.
- lithium iron phosphate eg, LiFePO 4 (LFP)
- composites of lithium iron phosphate and carbon lithium manganese phosphate (eg, LiMnPO 4 )
- LiMnPO 4 lithium manganese phosphate and carbon
- the positive electrode film layer also optionally includes a binder.
- binders that can be used in the positive film layer may include one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene tri- Element copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
- PVDF polyvinylidene fluoride
- PTFE polytetrafluoroethylene
- PTFE polytetrafluoroethylene
- PTFE polytetrafluoroethylene-propylene tri- Element copolymer
- vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer vinyliden
- the positive electrode film layer may also optionally contain a conductive agent.
- the conductive agent used in the positive electrode film layer may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
- the positive electrode can be prepared by dispersing the above-mentioned components for preparing the positive electrode, such as positive electrode active material, conductive agent, binder and any other components, in a solvent (such as N- Methylpyrrolidone), a uniform positive electrode slurry is formed; the positive electrode slurry is coated on the positive electrode current collector, and the positive electrode sheet can be obtained after drying, cold pressing and other processes.
- a solvent such as N- Methylpyrrolidone
- the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
- the electrolyte solution includes an electrolyte salt and a solvent.
- the electrolyte salt may be selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), bisfluorosulfonylidene Lithium Amide (LiFSI), Lithium Bistrifluoromethanesulfonimide (LiTFSI), Lithium Trifluoromethanesulfonate (LiTFS), Lithium Difluorooxalate Borate (LiDFOB), Lithium Dioxalate Borate (LiBOB), Lithium Difluorophosphate One or more of (LiPO 2 F 2 ), lithium difluorodioxalate phosphat
- the solvent may be selected from one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate ( DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC) ), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and Eth
- the content of the solvent is 60-99 wt %, for example, 65-95 wt %, or 70-90 wt %, or 75- 89% by weight, or 80-85% by weight. In an embodiment of the present application, based on the total weight of the electrolyte, the content of the electrolyte is 1-40 wt %, for example 5-35 wt %, or 10-30 wt %, or 11- 25% by weight, or 15-20% by weight.
- the electrolyte may optionally contain additives.
- the additives may include one or more of the following: negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performance of the battery, such as additives to improve battery overcharge performance, additives to improve battery high temperature performance, Additives to improve low temperature performance of batteries, etc.
- the battery cell further includes a separator, which separates the positive electrode piece and the negative electrode piece of the battery cell, and provides selective permeation to substances of different types, sizes and charges in the system. Or blocking, for example, the separator can insulate the electrons, physically isolate the positive and negative active materials of the cell, prevent the internal short circuit and form an electric field in a certain direction, and at the same time enable the ions in the battery to pass through the separator between the positive and negative electrodes. move between.
- a separator which separates the positive electrode piece and the negative electrode piece of the battery cell, and provides selective permeation to substances of different types, sizes and charges in the system. Or blocking, for example, the separator can insulate the electrons, physically isolate the positive and negative active materials of the cell, prevent the internal short circuit and form an electric field in a certain direction, and at the same time enable the ions in the battery to pass through the separator between the positive and negative electrodes. move between.
- the material used to prepare the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
- the separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different.
- the above-mentioned positive electrode sheet, negative electrode sheet and separator can be made into electrode assemblies/bare cell cores through a winding process or a lamination process.
- the battery cell further includes an outer package, and the outer package can be used to encapsulate the above-mentioned electrode assembly and the electrolyte.
- the outer packaging of the cell may be a hard case, such as a hard plastic case, an aluminum case, a steel case, and the like.
- the outer package of the battery cell may be a soft package, such as a bag-type soft package.
- the material of the soft bag may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), and the like.
- FIG. 1 is a schematic diagram showing one example of the battery cell 5 of the present application.
- FIG. 2 is an exploded view showing one example of the battery cell 5 of the present application shown in FIG. 1 .
- the outer package may include a casing 51 and a cover plate 53 , the casing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are enclosed to form a receiving cavity.
- the housing 51 has an opening that communicates with the accommodating cavity, and a cover plate 53 can cover the opening to close the accommodating cavity.
- the positive pole piece, the negative pole piece and the separator can be rolled or laminated to form the electrode assembly 52 , the electrode assembly is packaged in the accommodating cavity, and the electrolyte is infiltrated in the electrode assembly 52 .
- the number of electrode assemblies 52 included in the battery cell 5 may be one or more.
- a “battery pack” is formed by electrically connecting a certain number of cells together and putting them into a frame in order to protect the cells from external impact, heat, vibration, etc.
- the shape of the battery cell of the present application can be cylindrical, square or any other shape.
- the battery pack contains two or more cells, the specific number of which depends on the application of the battery pack and the parameters of a single battery pack.
- FIG. 3 is a schematic diagram showing one example of the battery pack of the present application.
- a plurality of cells 5a, 5b may be arranged in sequence along the length direction of the battery pack 4 (5a may be the first cell, 5b may be the second cell). Of course, it can also be arranged in any other manner. Further, the plurality of battery cells 5a and 5b can be fixed by fasteners.
- the battery pack 4 may further include a housing having an accommodating space, and the plurality of packs 5a, 5b are accommodated in the accommodating space.
- the battery pack includes at least a first type of battery cell and a second type of battery cell that are electrically connected in series, the first type of battery cell and the second type of battery cell are cells of different chemical systems, and the first type of battery cell and the second type of battery cell are cells of different chemical systems.
- One type of cell includes N first cells, the second type of cell includes M second cells, and N and M are positive integers; the first cell includes a first negative pole piece, and the first The second battery cell includes a second negative electrode pole piece.
- the ratio of the electrolyte conductivity (25°C) of the first battery core to the coating mass per unit area of the first negative electrode pole piece is denoted as M1, and the second battery core is denoted as M1.
- the ratio of the electrolyte conductivity (25°C) of the core to the coating mass per unit area of the second negative pole piece is denoted as M2, wherein the unit of the electrolyte conductivity is mS/cm, and the unit area coating
- M1 and M2 satisfy: M1>M2, 0.08 ⁇ M1 ⁇ 11, 0.03 ⁇ M2 ⁇ 4.62.
- the conductivity of the electrolyte may be represented by ⁇ (unit: mS/cm), and the coating mass per unit area of the negative electrode piece may be represented by CW (unit: mg/cm 2 ).
- the compaction density of the sheet is represented by PD (unit: g/cm 3 ), and the ratio of the conductivity of the electrolyte to the coating mass per unit area of the negative electrode sheet is expressed by M (M1 and M2 correspond to the first type of cells and The second type of cells) to represent.
- the inventors of the present application have found through painstaking research that the conductivity of the electrolyte is positively correlated with the lithium deposition window, the coating quality per unit area of the negative pole piece is negatively correlated with the lithium deposition window, and the conductivity of the electrolyte solution is positively correlated with the coating per unit area of the negative electrode piece.
- the first type of cell and the second type of cell are connected in series at least, when the ratio M1 of the conductivity of the electrolyte of the first cell to the coating mass per unit area of the first negative pole piece, and the electrolysis of the second cell
- M1>M2 the ratio M2 of the liquid conductivity to the coating mass per unit area of the second negative pole piece satisfies: M1>M2
- the lithium deposition window of the first cell can be made > the lithium deposition window of the second cell, which can be achieved in the battery pack.
- the first type of battery is not prone to safety problems such as lithium precipitation.
- FIG. 7 is a schematic diagram illustrating an example of a charging curve when the step charging of the first type of cells in the battery pack (taking lithium iron phosphate cells as an example) is controlled by voltage according to an embodiment of the present application.
- the second type of battery cell (for example, a ternary cell) is used to control the first type of battery cell (for example, a ternary battery cell).
- the first type of battery cell lithium iron phosphate battery cell
- the second type of battery cell for example, a ternary cell
- the accuracy of the step charging is higher, and the current SOC value of the first type of battery can be displayed more accurately. It can be realized that when the battery pack is charged by a ladder, the fast charging is safer, and the lithium precipitation problem of the first type of cells is not easy to occur.
- the first type of battery is charged with a constant current I1; after the first predetermined time elapses, when the OCV voltage of the second type of battery reaches V1, the charging current suddenly changes to I2, and the constant current The current I2 continues to be charged; after the second predetermined time elapses, when the OCV voltage of the second type of cell reaches V2, the charging current suddenly changes to I3, and continues to charge with the constant current I3; after the third predetermined time, the second When the OCV voltage of the second type cell reaches V3, the charging current suddenly changes to I4, and continues to charge with the constant current I4; when the OCV voltage of the second type cell reaches V4 after the fourth predetermined time, the charging current suddenly changes to I5 , and continue to charge with the constant current I5; when the OCV voltage of the second type cell reaches V5 after the fifth predetermined time, the charging current suddenly changes to I6, and continues to charge with the constant current I6 until the first type of battery is charged.
- the battery is full.
- the slope K2 of the SOC-OCV curve of the second type of cells is greater than the slope K1 of the SOC-OCV curve of the first type of cells, according to the second type of battery cells
- the OCV voltage of the cell is used to control the constant current charging current of the first type of battery, so the accuracy of the step charging is higher, so that the fast charging using the step charging can be safer and more reliable, and the first type of battery can be displayed more accurately.
- Current SOC value is used to control the constant current charging current of the first type of battery, so the accuracy of the step charging is higher, so that the fast charging using the step charging can be safer and more reliable, and the first type of battery can be displayed more accurately.
- SOC represents the state of charge (State Of Charge), which refers to the ratio of the remaining power of the current cell to the rated capacity under the same conditions, for example, it can be 100%, 99%, 90%, 80%, 70% , 60%, 50%, 40%, 30%, 20%, 10%, 0%.
- OCV stands for Open Circuit Voltage.
- making the electrolyte conductivity larger and the coating mass per unit area of the negative pole piece smaller can reduce the charge transfer resistance Rct and the diffusion resistance Rdiff (for example, when lithium ions are inserted and extracted, close to solid-phase diffusion in the negative electrode active material on the current collector side), thereby improving the kinetic characteristics of lithium ion transport in the first type of cells.
- the conductivity test of the electrolyte can be realized by directly selecting the conductivity electrode.
- the conductance is two parallel electrode sheets determined by the area A and the distance L, corresponding to the electrode conductance constant K.
- the conductance constant K needs to be calibrated with a standard solution before the test.
- the parallel electrodes are bright platinum electrodes or platinum black electrodes, which need to be selected in combination with the large conductivity of the electrolyte and the test range of different types of conductivity electrodes. Typically bright electrodes are used to measure smaller conductivities, while platinum black electrodes are used to measure larger conductivities.
- the platinum black electrode Due to the large surface area of the platinum black electrode, the current density is reduced to reduce or eliminate polarization; when measuring low-conductivity solutions, the platinum black electrode has a strong adsorption effect on the electrolyte, and the phenomenon of instability occurs. At this time, a bright platinum electrode should be used.
- aqueous electrolyte add an appropriate amount of electrolyte directly into the glass tube, and the amount of addition must ensure that the liquid level does not pass the electrode of the conductivity electrode; while the organic electrolyte needs to be tested in a glove box filled with high-purity argon gas, or Design the sealed container according to the needs, apply vacuum silicone grease or Vaseline to the interface position to achieve a better sealing effect, and finally complete the battery assembly.
- the electrical conductivity meter DDSJ-318 can be used to test the resistance of the electrolyte under the conditions of 25°C and AC impedance of 1kHz, and calculate the conductivity ⁇ of the electrolyte.
- the coating mass per unit area of the negative electrode plate is the meaning known in the art, which refers to the mass of the negative electrode active material layer on one side of the current collector per unit area, which can be measured by methods known in the art. For example, take a pole piece that has been coated on one side and has been cold-pressed, or it can be a pole piece that has been disassembled from the cell (if it is a pole piece coated on both sides, you can wipe off the active material layer on one side first) , punched into small discs with an area of S1, weighed the mass, denoted as m1; then soaked the active material layer on the surface of the above-mentioned pole piece with a solvent, peeled off all the surface of the current collector, and weighed the mass of the current collector, denoted as m2; finally, divide the mass of the active material layer (m1-m2) by the coating area S1 of the active material (ie (m1-m2)/S1), so as to obtain the coating mass per unit area of
- the state of charge-open circuit voltage (SOC-OCV) curve of the first cell satisfies at least one of the following conditions: (1) in the SOC range of 5%-95%, the first The slope k1 of the SOC-OCV curve of a battery cell is less than or equal to 5mV/% SOC; (2) in the SOC-OCV curve of the first battery cell, there is at least a section with a span of not less than 10% SOC and a slope of k1 ⁇ 5mV/% Flat curve of SOC.
- the state of charge-open circuit voltage (SOC-OCV) curve of the second cell satisfies at least one of the following conditions: (1) in the range of 5%-95% SOC, the The slope of the SOC-OCV curve of the second cell is k2>5mV/%SOC, optionally, k2 ⁇ 6mV/%SOC, further optionally, k2 ⁇ 9mV/%SOC; (2) the second cell In the SOC-OCV curve of , there is at least a section of the curve whose span is not less than 10% SOC and slope k2 > 5mV/% SOC.
- the slope of the SOC-OCV curve can be tested using a testing method known in the art.
- the following steps can be used to test:
- the compaction density of the first negative pole piece is PD1
- the compaction density of the second negative pole piece is PD2, where PD1 ⁇ PD2, and 0.5 ⁇ PD1 ⁇ 3, 0.5 ⁇ PD2 ⁇ 3, the unit is g/cm 3 .
- the inventor of the present application found through intensive research that the lithium deposition window, the charge transfer resistance Rct and the diffusion resistance Rdiff are also related to the compaction density of the negative pole piece (the diffusion resistance Rdiff has a greater influence).
- the higher the compaction density the tighter the particles are packed.
- the infiltration effect of the electrolyte becomes worse, the migration path between the negative active materials (such as graphite) becomes smaller, and the opportunity for liquid phase diffusion becomes smaller; on the other hand, the The stacking gap becomes smaller and the ion diffusion path becomes narrower, so that the insertion and extraction of lithium ions become difficult, resulting in a smaller lithium deposition window.
- the compaction density of the negative pole piece can be tested by a method known in the art.
- the coating mass per unit area of the first negative pole piece is CW1
- the coating mass per unit area of the second negative pole piece is CW2, where 6.49 ⁇ CW1 ⁇ 17, 4.54 ⁇ CW2 ⁇ 25.51, unit: mg/cm 2 .
- the inventors of the present application have found through intensive research that the coating quality of the active material layer of the negative electrode pole piece needs to be controlled within an appropriate range.
- the material layer is polarized to improve the power performance of the cell; on the other hand, it can ensure the high energy density of the cell and the module, and reduce the manufacturing cost of the cell per watt-hour.
- the negative poles in the first type of battery cell and the second type of battery cell can be realized by optimizing the design.
- the lithium ion diffusion path and capacity characteristics of the chip are effectively compatible, thereby further improving the volumetric energy density and fast charging safety of the battery pack.
- the negative active material of the first negative electrode and the negative active material of the second negative electrode can be independently selected from artificial graphite, natural graphite, soft carbon, hard carbon, silicon One or more of base materials, tin-based materials, and lithium titanate.
- the ratio of the number N of the first battery cells to the number M of the second battery cells is 0.1-50, optionally 0.3-30, and further optionally 0.5- 10.
- two or more of the above-mentioned battery packs may be assembled into a battery pack, and the number of battery packs contained in the battery pack depends on the application of the battery pack and the parameters of a single battery pack.
- the battery pack may include a battery box and a plurality of battery packs arranged in the battery box, the battery box includes an upper box body and a lower box body, the upper box body can be covered on the lower box body and is well matched with it, and is formed for accommodating batteries Group of enclosed spaces.
- Two or more battery packs can be arranged in the battery box in a desired manner.
- a "battery pack" is made by further assembling various control and protection systems such as a battery management system and a thermal management system for one or more battery packs (or a combination directly formed by a plurality of cells).
- FIG. 4 is a schematic diagram showing one example of the battery pack 1 of the present application.
- FIG. 5 is an exploded view showing one example of the battery pack 1 of the present application shown in FIG. 4 .
- the battery pack 1 may include a battery case and a plurality of battery packs 4 provided in the battery case.
- the battery box includes an upper box body 2 and a lower box body 3 .
- the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery pack 4 .
- the plurality of battery packs 4 can be arranged in the battery case in any manner.
- the electrical device of the present application includes at least one of the battery pack or the battery pack of the present application, and the battery pack or the battery pack can be used as a power source of the electrical device, It can also be used as an energy storage unit for the electrical consumer.
- the electrical devices include but are not limited to mobile digital devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric Golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
- FIG. 6 is a schematic diagram showing an example of a power consumption device using the battery pack of the present application as a power source.
- the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
- a battery pack or battery pack can be used.
- the present application proposes a method for manufacturing a battery pack, which includes the following steps: obtaining a first type of battery cell and a second type of battery cell, wherein the first type of battery cell and the second type of battery cell are batteries of different chemical systems, so
- the first type of battery includes N first batteries
- the second type of battery includes M second batteries
- N and M are positive integers
- the first battery includes a first negative pole piece
- the second battery core includes a second negative electrode pole piece
- the ratio of the electrolyte conductivity (25° C.) of the first battery core to the coating mass per unit area of the first negative electrode pole piece is denoted as M1
- the first battery core is marked as M1.
- the ratio of the electrolyte conductivity (25°C) of the second cell to the coating mass per unit area of the second negative pole piece is denoted as M2, wherein the unit of the electrolyte conductivity is mS/cm, and the unit area
- M1 and M2 satisfy: M1>M2, and 0.08 ⁇ M1 ⁇ 11, 0.03 ⁇ M2 ⁇ 4.62; Electrically connected at least in series to form a battery pack as described above.
- the present application proposes a manufacturing equipment for a battery pack, comprising: a clamping arm unit, the clamping arm unit is used to obtain a first type of battery cell and a second type of battery cell, the first type of battery cell and the second type of battery cell are cells of different chemical systems, the first type of cells includes N first cells, the second type of cells includes M second cells, N and M are positive integers, the first cell
- the core includes a first negative pole piece, the second battery core includes a second negative pole piece, the electrolyte conductivity (25°C) of the first battery core and the coating quality per unit area of the first negative pole piece
- the ratio is recorded as M1
- the ratio of the electrolyte conductivity (25°C) of the second battery core to the coating mass per unit area of the second negative pole piece is recorded as M2, wherein the unit of the electrolyte conductivity is is mS/cm, the unit of the coating mass per unit area is mg/cm 2 , M1 and M2 satisfy: M1>M2,
- the battery pack manufactured using the manufacturing method and manufacturing apparatus of the present application can realize the fast charging capability and safety during the fast charging process of the battery pack containing cells of different types of chemical systems.
- the weight ratio of the positive electrode active material to the conductive carbon (there may be more than one conductive carbon), the binder polyvinylidene fluoride (PVDF) and other positive electrode additives according to the design target (the ratio here is not fixed, it can be carried out according to the needs) is in an appropriate amount.
- the N-methylpyrrolidone (abbreviated as NMP) solvent is fully stirred and mixed to form a uniform and stable slurry with a viscosity of 5000-30000mPa ⁇ s. The slurry will not gel or delaminate within 24 hours of standing. or subsidence.
- the positive electrode slurry is uniformly coated on the positive electrode current collector Al foil, so that the coating weight of the membrane sheet per unit area after drying reaches the set value, and the polar sheet is cold-pressed to achieve the design compaction, and it is divided into strips for use to obtain a positive electrode. piece.
- electrolyte preparation the electrolyte can be adjusted according to the design requirements, the solvent, salt and additives: Dissolve an equal volume of ethylene carbonate in propylene carbonate, and then evenly dissolve an appropriate amount of lithium hexafluorophosphate in the The mixed solvent is used for later use, and electrolyte additives are added according to the design, and the electrolyte is obtained after fully dissolving and uniform.
- the isolation film with PP as the main material is selected as the cell isolation film.
- the positive pole piece, the separator and the negative pole piece are wound together to form a bare cell, then placed in the battery case, injected with electrolyte, followed by formation, sealing and other processes, and finally obtained Rechargeable power cells.
- the battery pack is a first-type cell and a second-type cell that are electrically connected in series, the first-type cell and the second-type cell are cells of different chemical systems, and the first-type cell includes 7 There are two first batteries, and the second type of batteries includes two second batteries, which are arranged and assembled in the manner of BAAAAAAB (wherein A represents the first battery, and B represents the second battery).
- the electrical conductivity meter DDSJ-318 was used to test the resistance of the electrolyte under the conditions of 25 °C and AC impedance of 1 kHz, and calculate the conductivity ⁇ of the electrolyte.
- Three-electrode production reference standard production, adding a lithium-plated electrode as a reference electrode based on a single-laminate production process;
- Lithium precipitation window test The corresponding lithium precipitation window is obtained by the three-electrode test of the second type of cell system.
- the specific test process is as follows:
- V1-V2 lower limit voltage - upper limit voltage
- a typical test current selection principle X>3C, take a point test every 1C; 1C ⁇ X ⁇ 3C, take a point test every 0.5C; X ⁇ 1C, take a point every 0.2C.
- Hard case verification comparison According to the lithium deposition window obtained by the test, formulate the above charging strategy, charge and discharge the first and second types of cells at 25°C according to the above charging strategy for 10 times, and disassemble the first battery pack in a fully charged state. A type of battery cell and a second type of battery cell, comparing the lithium deposition of the anode.
- Lithium precipitation grade I no lithium precipitation, no white lithium precipitation area on the surface of the disassembled fully charged anode, and the proportion of the total lithium precipitation area is less than 0.1%;
- Lithium precipitation grade II slight precipitation of lithium, there are white dots of lithium precipitation on the surface of the fully charged anode, or a small amount of strip-shaped lithium precipitation area, and the total area of lithium precipitation accounts for 0.1% to 0.5%;
- Lithium precipitation grade III moderate lithium precipitation, dismantling the fully charged anode surface with white dotted lithium precipitation, strip-shaped lithium precipitation area, or block and flake lithium precipitation, the total lithium precipitation area accounts for 0.5-5%;
- Lithium precipitation grade IV Lithium precipitation is severe, and the surface of the fully charged anode has white dots, strip precipitation, or block and flake lithium precipitation, and the total precipitation area accounts for ⁇ 5%;
- the degree of lithium precipitation I and II are qualified (due to the special position of the battery cell and the slight lithium precipitation caused by the fluctuation of the manufacturing process in the design of the hard case winding), and the grades III and IV are considered to be unqualified for fast charging.
- the battery packs of the following Examples 1 to 13 and the battery packs of Comparative Examples 1 and 2 were obtained by the above-mentioned "Cell Preparation" method.
- the first type of batteries adopts lithium iron phosphate system batteries (LFP)
- the second type of batteries adopts nickel-cobalt lithium manganate 523 system batteries (NCM523 ).
- the charge and discharge range of the second type of battery is 2.8 to 4.35V
- the charge and discharge range of the second type of battery is 2.8 to 4.4V
- Example 13 the second battery
- the charge-discharge range of the cell-like cell is 2.8-3.8V.
- the battery packs of Examples 1 to 5 include first-type cells and second-type cells that are electrically connected in series, and the first-type cells and second-type cells are of different chemical systems Cells, the first cell includes a first negative pole piece, the second cell includes a second negative pole piece, the electrolyte conductivity (25°C) of the first cell and the coating quality per unit area of the first negative pole piece
- M1 the ratio of the electrolyte conductivity (25°C) of the second cell to the coating mass per unit area of the second negative pole piece
- M2 the unit of electrolyte conductivity is mS/cm
- the unit The unit of area coating mass is mg/cm 2
- M1 and M2 satisfy: M1>M2, and 0.08 ⁇ M1 ⁇ 11, 0.03 ⁇ M2 ⁇ 4.62.
- the inventors of the present application found that: the conductivity of the electrolyte is positively correlated with the lithium deposition window, the coating mass per unit area of the negative pole piece is negatively correlated with the lithium deposition window, and the ratio of the conductivity of the electrolyte to the coating mass per unit area of the negative electrode piece is M The larger the value, the larger the lithium deposition window.
- the first cell and the second cell satisfy: M1>M2, and 0.08 ⁇ M1 ⁇ 11, 0.03 ⁇ M2 ⁇ 4.62
- the compaction density PD1 of one negative pole piece and the compaction density of the second negative pole piece are PD2 and satisfy: PD1 ⁇ PD2, and 0.5 ⁇ PD1 ⁇ 3, 0.5 ⁇ PD2 ⁇ 3 (unit is g/cm 3 )
- the active material particles in the negative pole pieces of the first cell and the second cell are tightly packed and have a certain ion diffusion path, which can ensure the high volumetric energy density of the battery pack, while the first cell and the second cell are
- the respective lithium deposition windows of the cores are relatively large, which can effectively reduce the risk of lithium deposition in the fast charging process.
- the first cell and the second cell satisfy: M1>M2, and 0.08 ⁇ M1 ⁇ 11, 0.03 ⁇ M2 ⁇ 4.62 on the basis of the first cell
- the coating mass CW1 per unit area of one negative pole piece and the coating mass CW2 per unit area of the second negative pole piece also satisfy: 6.49 ⁇ CW1 ⁇ 17, 4.54 ⁇ CW2 ⁇ 25.51 (unit: mg/cm 2 )
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Abstract
本申请涉及一种电池组,所述电池组包括至少以串联形式电连接的第一类电芯和第二类电芯,所述第一类电芯和第二类电芯为不同的化学体系电芯,所述第一类电芯包括N个第一电芯,所述第二类电芯包括M个第二电芯,N和M为正整数;所述第一电芯包括第一负极极片,所述第二电芯包括第二负极极片,所述第一电芯的电解液电导率(25℃)与所述第一负极极片的单位面积涂布质量的比值记为M1,所述第二电芯的电解液电导率(25℃)与所述第二负极极片的单位面积涂布质量的比值记为M2,其中所述电解液电导率的单位为mS/cm,所述单位面积涂布质量的单位为mg/cm 2,M1和M2满足:M1>M2,且0.08≤M1≤11,0.03≤M2≤4.62。
Description
本申请涉及储能器件技术领域,尤其涉及一种电池组、电池包、电学装置以及电池组的制造方法和电池组的制造设备。
二次电池具有体积小、能量密度高、功率密度高、循环使用次数多和存储时间长等优点,在一些电子设备、电动交通工具、电动玩具和电动设备上应用广泛,例如手机、笔记本电脑、电瓶车、电动汽车、电动飞机、电动轮船、电动玩具汽车、电动玩具轮船、电动玩具飞机和电动工具等。
二次电池作为新能源汽车的动力驱动电源或储能电站的大容量存储单元,需要将多个电芯进行串/并联得到电池组、电池包、或***电柜。为了提高二次电池的安全性,提出了一种将多个不同化学体系的电芯进行连接、以形成电池组的技术方案,其中一类电芯例如为具有高能量密度的含锂镍钴锰酸锂金属氧化物的三元电芯,另一类电芯例如为具有较高安全性的磷酸铁锂电芯。
然而,不同化学体系的电芯,其能量密度、充放电特性以及高低温特性等均具有显著差异,不同化学体系的电芯之间如何匹配,才能实现电池组兼顾快速充放电能力及较高的安全性,是二次电池领域一项急需解决的技术问题。
发明内容
在现有技术中,仅仅记载了将多个种类的电芯进行连接,而完全没有记载电池组的与充电策略相关的设计关键参数的合理范围,同时对于不同种类电芯的快速充放电过程的安全性如何实现并没有任何记载和披露。
本申请是鉴于现有技术中存在的上述问题而完成的,其目的在于,提供一种电池组,通过对不同种类电芯的各个参数进行匹配设计,从而可保证不同充放电特性的电芯能统一进行快速充放电且快充过程中不易发生析锂等安全问题。
本申请的第一方面提供一种电池组,所述电池组包括至少以串联形式电连接的第一类电芯和第二类电芯,所述第一类电芯和第二类电芯为不同的化学体系电芯,所述第一类电芯包括N个第一电芯,所述第二类电芯包括M个第二电芯,N和M为正整数;所述第一电芯包括第一负极极片,所述第二电芯包括第二负极极片,所述第一电芯的电解液电导率(25℃)与所述第一负极极片的单位面积涂布质量的比值记为M1,所述第二电芯的电解液电导率(25℃)与所述第二负极极片的单位面积涂布质量的比值记为M2,其中所述电解液电导率的单位为mS/cm,所述单位面积涂布质量的单位为mg/cm
2,M1和M2满足:M1>M2,且0.08≤M1≤11,0.03≤M2≤4.62。
可选地,0.33≤M1≤6.42,0.17≤M2≤2.57。进一步可选地,0.63≤M1≤1.94,0.63≤M2≤1.1。
可选地,所述第一电芯的荷电状态-开路电压(SOC-OCV)曲线至少满足以下条件之一:(1)在5%-95%SOC区间,所述第一电芯的SOC-OCV曲线的斜率k1≤5mV/%SOC;(2)所述第一电芯的SOC-OCV曲线中,至少存在一段跨度不低于10%SOC、斜率k1≤5mV/%SOC的平缓曲线。
可选地,所述第二电芯的荷电状态-开路电压(SOC-OCV)曲线至少满足以下条件之一:(1)在5%-95%SOC的区间,所述第二电芯的SOC-OCV曲线的斜率k2>5mV/%SOC,可选地,k2≥6mV/%SOC,进一步可选地,k2≥9mV/%SOC;(2)所述第二电芯的SOC-OCV曲线中,至少存在一段跨度不低于10%SOC、斜率k2>5mV/%SOC的曲线。
可选地,所述第一负极极片的压实密度为PD1,所述第二负极极片的压实密度为PD2,其中,PD1<PD2,且0.5≤PD1≤3,0.5≤PD2≤3,单位为g/cm
3;可选地,1≤PD1≤2,1≤PD2≤2;进一步可选地,1.2≤PD1≤1.7,1.2≤PD2≤1.7。
可选地,所述第一负极极片的单位面积涂布质量为CW1,所述第二负极极片的单位面积涂布质量为CW2,其中,6.49≤CW1≤17,4.54≤CW2≤25.51,单位为:mg/cm
2。可选地,7.79≤CW1≤11.69,6.23≤CW2≤15.19。进一步可选地,9.09≤CW1≤11.04,7.73≤CW2≤12.69。更进一步可选地,CW1<CW2。
可选地,所述第一负极极片的负极活性物质和所述第二负极极片的负极活性物质可以独立的选自人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料、钛酸 锂中的一种或几种。
可选地,所述第一电芯的数量N与所述第二电芯的数量M之比为0.1~50,可选地为0.3~30,进一步可选地为0.5~10。
本申请的第二方面提供一种电池包,其特征在于,包括上述第一方面所述的电池组。
本申请的第三方面提供一种用电装置,包括上述第一方面所述的电池组或者包括上述第二方面所述的电池包,且所述电池组或者所述电池包可以作为所述用电装置的电源或者能量存储单元。
本申请的第四方面提供一种电池组的制造方法,包括如下步骤:获取第一类电芯和第二类电芯,所述第一类电芯和第二类电芯为不同的化学体系电芯,所述第一类电芯包括N个第一电芯,所述第二类电芯包括M个第二电芯,N和M为正整数,所述第一电芯包括第一负极极片,所述第二电芯包括第二负极极片,所述第一电芯的电解液电导率(25℃)与所述第一负极极片的单位面积涂布质量的比值记为M1,所述第二电芯的电解液电导率(25℃)与所述第二负极极片的单位面积涂布质量的比值记为M2,其中所述电解液电导率的单位为mS/cm,所述单位面积涂布质量的单位为mg/cm
2,M1和M2满足:M1>M2,且0.08≤M1≤11,0.03≤M2≤4.62;以及将所述第一类电芯和所述第二类电芯至少串联的方式电连接,以形成上述第一方面所述的电池组。
本申请的第五方面提供电池组的制造设备,包括:夹臂单元,所述夹臂单元用于获取第一类电芯和第二类电芯,所述第一类电芯和第二类电芯为不同的化学体系电芯,所述第一类电芯包括N个第一电芯,所述第二类电芯包括M个第二电芯,N和M为正整数,所述第一电芯包括第一负极极片,所述第二电芯包括第二负极极片,所述第一电芯的电解液电导率(25℃)与所述第一负极极片的单位面积涂布质量的比值记为M1,所述第二电芯的电解液电导率(25℃)与所述第二负极极片的单位面积涂布质量的比值记为M2,其中所述电解液电导率的单位为mS/cm,所述单位面积涂布质量的单位为mg/cm
2,M1和M2满足:M1>M2,且0.08≤M1≤11,0.03≤M2≤4.62;组装单元,所述组装单元用于将所述第一类电芯和所述第二类电芯以至少串联的方式电连接,以形成上述第一方面所述的电池组;以及控制单元,该控制单元用于控制所述夹臂单元和所述组装单元。
[技术效果]
本申请中,电池组包括至少以串联连接的、不同化学体系的第一类电芯及第二类电芯,通过将所述第一类电芯的电解液电导率与所述第一负极极片的单位面积涂布质量的比值、以及所述第二类电芯的电解液电导率与所述第二负极极片的单位面积涂布质量的比值进行优化设计,保证第一类电芯与第二类电芯的析锂窗口匹配,从而可实现对含有不同化学体系电芯的电池组具有良好的快速充放电能力且快充过程中不易发生析锂。
本申请的电池包和装置包括所述的电池模组,因而至少具有与所述电池组相同的技术优势。
图1是示出本申请的电芯的一个示例的示意图。
图2是示出图1所示的本申请的电芯的一个示例的分解图。
图3是示出本申请的电池组的一个示例的示意图。
图4是示出本申请的电池包的一个示例的示意图。
图5是示出图4所示的本申请的电池包的一个示例的分解图。
图6是示出将本申请的电池组用作电源的用电装置的一个示例的示意图。
图7是示出使用本申请实施方式的通过电压来控制对电池组中的第一类电芯(磷酸铁锂电芯)进行的阶梯充电时的充电曲线的示例的示意图。
图8是示出现有技术中根据SOC值来控制磷酸铁锂电芯的阶梯充电时的充电曲线的示意图。
标号说明
5、5a、5b 电芯
51 壳体
52 电极组件
53 盖板
4 电池组
1 电池包
2 上箱体
3 下箱体
本文所公开的“范围”以下限和上限的形式来限定,给定范围是通过选定一个下限和一个上限进行限定的,选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的,并且可以进行任意地组合,即任何下限可以与任何上限组合形成一个范围。例如,如果针对特定参数列出了60-120和80-110的范围,理解为60-110和80-120的范围也是预料到的。此外,如果列出的最小范围值1和2,和如果列出了最大范围值3,4和5,则下面的范围可全部预料到:1-3、1-4、1-5、2-3、2-4和2-5。在本申请中,除非有其他说明,数值范围“a-b”表示a到b之间的任意实数组合的缩略表示,其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数,“0-5”只是这些数值组合的缩略表示。另外,当表述某个参数为≥2的整数,则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
在本申请中,如果没有特别的说明,本文所提到的所有实施方式以及优选实施方式可以相互组合形成新的技术方案。
在本申请中,如果没有特别的说明,本文所提到的所有技术特征以及优选特征可以相互组合形成新的技术方案。
在本申请中,如果没有特别的说明,本文所提到的所有步骤可以顺序进行,也可以随机进行,但是优选是顺序进行的。例如,所述方法包括步骤(a)和(b),表示所述方法可包括顺序进行的步骤(a)和(b),也可以包括顺序进行的步骤(b)和(a)。例如,所述提到所述方法还可包括步骤(c),表示步骤(c)可以任意顺序加入到所述方法,例如,所述方法可以包括步骤(a)、(b)和(c),也可包括步骤(a)、(c)和(b),也可以包括步骤(c)、(a)和(b)等。
在本申请中,如果没有特别的说明,本文所提到的“包括”和“包含”表示开放式,也可以是封闭式。例如,所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分,也可以仅包括或包含列出的组分。
在本文的描述中,需要说明的是,除非另有说明,“以上”、“以下”为包含本数,“一种或几种”中“几种”的含义是两种及两种以上。
在本文的描述中,除非另有说明,术语“或”是包括性的。举例来说,短语“A或B”表示“A,B,或A和B两者”。更具体地,以下任一条件均满足条件“A或B”:A为真(或存在)并且B为假(或不存在);A为假(或不存在)而B为真(或存在);或A和B都为真(或存在)。
二次电池作为新能源汽车的动力驱动电源或储能电站的大容量存储单元,除了需要具有较高的能量密度以外,人们对于二次电池充电速度的要求也不断提高。
为了实现二次电池的快速充电,当前普遍使用阶梯式充电的方式。上述阶梯式充电的充电曲线通常由多个台阶组成,在每一个台阶以恒定的电流持续充电一定时间,然后在下一个临界点,充电电流提高,在下一个台阶继续以恒定的电流进行充电。阶梯式充电一般根据二次电池的负极极片对应的析锂窗口(体现为电芯不同SOC下所对应的最大充电电流)进行调控。
但是,当电池组中包括多个不同化学体系的电芯以串联连接,对其以相同的电流进行充电时,由于不同化学体系电芯的充放电特性差异显著,如何实现不同化学体系的电芯统一进行快速充放电且安全性较高成为一个技术难题。
[电芯]
本申请中,“电芯”是指能够独立进行充放电的电池单体。电芯包括正极极片、负极极片、隔膜、电解液以及用于封装正极极片、负极极片、隔膜和电解液的外包装等。本申请对电芯的类型、形状没有特别的限制,其可以是软包电芯,也可以是柱形电芯、或是方形电芯等各类电芯。本申请中的电芯可以是锂离子电芯、钾离子电芯、钠离子电芯、锂硫电芯等,特别优选是锂离子电芯。在电池单体的充放电过程中,活性离子在正极极片和负极极片之间往返嵌入和脱出。电解液在正极极片和负极极片之间起到传导离子的作用。
本申请中,“电芯”是指能够独立进行充放电的电池单体。电芯的组成构件可以包括正极极片、负极极片、隔膜、电解液以及用于封装正极极片、负极极片、隔膜和电解液的外包装等。本申请对电芯的类型、形状没有特别的限制,其可以是软包电芯,也可以是柱形电芯、或是方形电芯等各类电芯。本申请中的电芯可以是锂离子电芯、钾离子电芯、钠离子电芯、锂硫电芯等,特别优选是锂离子电芯。在电池充放电过程中,活性离子在正极极片和负极极片之间往返嵌入和脱出。电解液在正极极片和负极极片之间起到传导离子的作用。
本申请中,电芯的“化学体系”是按照电芯中正极极片所使用的正极活性材料的组分进行划分,对正极活性材料的掺杂或包覆的元素或物质不作限定。例如,正极活性材料为磷酸铁锂(包括经Mn或V元素掺杂)的电芯均可以定义为磷酸铁锂化学体系电芯。正极活性材料为镍钴锰酸锂(一般简称NCM)的电芯可以定义为NCM化学体系电芯。进一步地,可以依据正极活性材料中镍、钴、锰元素的相对含量,对电芯化学体系进一步限定,如,正极活性材料为LiNi
0.5Co
0.2Mn
0.3O
2(一般简称NCM523)的电芯可以定义为NCM523化学体系电芯,正极活性材料为LiNi
0.6Co
0.2Mn
0.2O
2(一般简称NCM622)的电芯可以定义为NCM622化学体系电芯,正极活性材料为LiNi
0.8Co
0.1Mn
0.1O
2(一般简称NCM811)的电芯可以定义为NCM811化学体系电芯。镍钴铝酸锂体系电芯(一般称NCA)为正极材料的电芯可以定义为NCA化学体系电芯。此外,本申请中,也可采用混合体系电芯,例如包括NCM和NCA的混合体系电芯。
下面,首先对本申请中的电芯所具备的负极极片、正极极片、电解液、隔膜的基本结构进行说明。
<负极极片>
本申请的电芯中包括负极极片,所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面上的负极膜层,所述负极膜层包含负极活性材料。
在本申请的一个实施方式中,负极膜层中的负极活性材料,可以是本领域常用的负极活性材料,例如,天然石墨、人造石墨、软炭、硬炭、硅基材料、锡基材料、钛酸锂中的一种或几种。所述硅基材料可选自单质硅、硅氧化物、硅碳复合物中的一种或几种。所述锡基材料可选自单质锡、锡氧化合物、锡合金中的一种或几种。
本申请的电芯中,所述负极膜片中除包含负极活性材料外,还可以进一步包含可选的粘结剂、可选的导电剂和其他可选助剂。本申请的负极膜片,通常是由负极浆料涂布干燥而成的。负极浆料通常是将负极活性材料以及可选的导电剂和粘结剂等分散于溶剂中并搅拌均匀而形成的。上述溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水。
作为示例,导电剂可包括超导碳、炭黑(例如乙炔黑、科琴黑)、碳点、碳纳米管、石墨烯及碳纳米纤维中一种或几种。
作为示例,粘结剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、聚丙 烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)和羧甲基壳聚糖(CMCS)中的一种或几种。作为示例,粘结剂可包括丁苯橡胶(SBR)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的一种或几种。其他可选助剂例如是增稠剂(如羧甲基纤维素钠CMC-Na)、PTC热敏电阻材料等。
另外,本申请的电芯中,负极极片并不排除除了负极膜层之外的其他附加功能层。例如在某些实施方式中,本申请的负极极片还可包括夹在负极集流体和第一负极膜层之间、设置于负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施方式中,本申请的负极极片还可包括覆盖在第二负极膜层表面的覆盖保护层。
本申请的电芯中,所述负极集流体可以是金属箔片或复合集流体,例如金属箔片可以是铜箔、银箔、铁箔、或者上述金属的合金构成的箔片。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层,可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基层(如聚丙烯PP、聚对苯二甲酸乙二醇酯PET、聚对苯二甲酸丁二醇酯PBT、聚苯乙烯PS、聚乙烯PE及其共聚物等材料制成的基层)上而形成。
<正极极片>
本申请的电芯中,正极极片包括正极集流体以及设置在正极集流体至少一个表面且包括正极活性材料的正极膜层。例如,正极集流体具有在自身厚度方向相背的两个表面,正极膜层设置于正极集流体的两个相背表面中的任意一者或两者上。本申请的电芯中,所述正极集流体可以是金属箔片或复合集流体,例如所述金属箔片可以是铝箔,而所述复合集流体可包括高分子材料基层和形成于该高分子材料基层至少一个表面上的金属层。所述复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯PP、聚对苯二甲酸乙二醇酯PET、聚对苯二甲酸丁二醇酯PBT、聚苯乙烯PS、聚乙烯PE及其共聚物等的基材)上而形成。
在本申请的电芯中,所述正极活性材料可采用本领域公知的用于电芯的正极活性材料。例如,该正极活性材料可包括以下的一种或多种:橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料,还 可以使用其他可被用作电芯正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种,也可以将两种以上组合使用。其中,锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO
2)、锂镍氧化物(如LiNiO
2)、锂锰氧化物(如LiMnO
2、LiMn
2O
4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi
1/3Co
1/3Mn
1/3O
2(NCM333)、LiNi
0.5Co
0.2Mn
0.3O
2(NCM523)、LiNi
0.5Co
0.25Mn
0.25O
2(NCM211)、LiNi
0.6Co
0.2Mn
0.2O
2(NCM622)、LiNi
0.8Co
0.1Mn
0.1O
2(NCM811))、锂镍钴铝氧化物(如LiNi
0.85Co
0.15Al
0.05O
2)及其改性化合物等中的一种或几种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO
4(LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO
4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的一种或几种。
在一些实施方式中,正极膜层还可选地包括粘结剂。可用于正极膜层的粘结剂的非限制性例子可以包括以下的一种或多种:聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂。
在一些实施方式中,正极膜层还可任选地包含导电剂。用于正极膜层的导电剂的例子可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种或几种。
在本申请的一个实施方式中,可以通过以下方式制备正极:将上述用于制备正极的组分,例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中,形成均匀的正极浆料;将正极浆料涂覆在正极集流体上,经烘干、冷压等工序后,即可得到正极极片。
<电解液>
电解液在正极极片和负极极片之间起到传导离子的作用。所述电解液包括电解质盐和溶剂。在一些实施方式中,电解质盐可选自六氟磷酸锂(LiPF
6)、四氟硼酸锂(LiBF
4)、高氯酸锂(LiClO
4)、六氟砷酸锂(LiAsF
6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO
2F
2)、二氟二草酸磷酸锂(LiDFOP)及四氟草酸磷酸锂(LiTFOP)中的一种或几种。
在本申请的一个实施方式中,溶剂可选自以下的一种或多种:碳酸亚乙酯(EC)、 碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)。
在本申请的一个实施方式中,以所述电解液的总重量为基准计,所述溶剂的含量为60-99重量%,例如65-95重量%,或者70-90重量%,或者75-89重量%,或者80-85重量%。在本申请的一个实施方式中,以所述电解液的总重量为基准计,所述电解质的含量为1-40重量%,例如5-35重量%,或者10-30重量%,或者11-25重量%,或者15-20重量%。
在本申请的一个实施方式中,所述电解液中还可任选地包含添加剂。例如添加剂可以包括以下的一种或多种:负极成膜添加剂、正极成膜添加剂,还可以包括能够改善电池某些性能的添加剂,例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温性能的添加剂等。
<隔离膜>
在本申请的一个实施方式中,所述电芯还包括隔离膜,隔离膜将电芯的正极极片与负极极片隔开,对体系内不同种类、尺寸和电荷的物质提供选择性透过或阻隔,例如隔离膜可以对电子绝缘,将电芯的正负极活性物质物理隔离,防止内部发生短路并形成一定方向的电场,同时使得电池中的离子能够穿过隔离膜在正负极之间移动。
在本申请的一个实施方式中,用来制备隔离膜的材料可包括玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种或几种。隔离膜可以是单层薄膜,也可以是多层复合薄膜。隔离膜为多层复合薄膜时,各层的材料可以相同或不同。
在本申请的一个实施方式中,上述正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件/裸电芯。
在本申请的一个实施方式中,电芯还包括外包装,该外包装可用于封装上述电极组件及电解液。在一些实施方式中,电芯的外包装可以是硬壳,例如硬塑料壳、铝壳、钢壳等。在另一些实施方式中,所述电芯的外包装可以是软包,例如袋式软 包。软包的材质可以是塑料,如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的一种或几种。
图1是示出本申请的电芯5的一个示例的示意图。图2是示出图1所示的本申请的电芯5的一个示例的分解图。
所述外包装可包括壳体51和盖板53,壳体51可包括底板和连接于底板上的侧板,所述底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口,盖板53能够盖设于所述开口,以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52,该电极组件封装于所述容纳腔中,所述电解液浸润于电极组件52中。电芯5所含电极组件52的数量可以为一个或多个。
[电池组]
本申请中,“电池组”是为了保护电芯免受外部冲击、热、振动等影响,将一定数目的电芯电连接在一起并放入一个框架中而形成的。本申请的电芯的形状可以是圆柱形、方形或其他任意的形状。
本申请中,可以将若干个电芯组装在一起以构成电池组,电池组中包含两个或更多个电芯,具体数量取决于电池组的应用和单个电池组的参数。
图3是示出本申请的电池组的一个示例的示意图。参照图3,在电池组4中,多个电芯5a、5b可以是沿电池组4的长度方向依次排列设置(其中5a可以为第一电芯,5b可以为第二电芯)。当然,也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个电芯5a、5b进行固定。可选地,电池组4还可以包括具有容纳空间的外壳,多个组5a、5b容纳于该容纳空间。
<关于第一类电芯与第二类电芯的设计>
本申请中,电池组包括至少以串联形式电连接的第一类电芯和第二类电芯,所述第一类电芯和第二类电芯为不同的化学体系电芯,所述第一类电芯包括N个第一电芯,所述第二类电芯包括M个第二电芯,N和M为正整数;所述第一电芯包括第一负极极片,所述第二电芯包括第二负极极片,所述第一电芯的电解液电导率(25℃)与所述第一负极极片的单位面积涂布质量的比值记为M1,所述第二电芯的电解液电导率(25℃)与所述第二负极极片的单位面积涂布质量的比值记为M2,其 中所述电解液电导率的单位为mS/cm,所述单位面积涂布质量的单位为mg/cm
2,M1和M2满足:M1>M2,0.08≤M1≤11,0.03≤M2≤4.62。
在本申请的一些实施方式中,0.33≤M1≤6.42,0.17≤M2≤2.57。可选地,0.63≤M1≤1.94,0.63≤M2≤1.1。
以下,为了方便说明,有时将电解液电导率用σ(单位:mS/cm)来表示,将负极极片的单位面积涂布质量用CW(单位:mg/cm
2)来表示,将负极极片的压实密度用PD(单位:g/cm
3)来表示,将电解液电导率与负极极片的单位面积涂布质量的比值用M(M1和M2分别对应于第一类电芯和第二类电芯)来表示。
本申请的发明人通过潜心研究发现:电解液电导率与析锂窗口正相关,负极极片的单位面积涂布质量与析锂窗口负相关,电解液电导率与负极极片的单位面积涂布质量的比值M越大,则析锂窗口越大。由于第一类电芯和第二类电芯至少以串联连接,当第一电芯的电解液电导率与第一负极极片的单位面积涂布质量的比值M1、和第二电芯的电解液电导率与第二负极极片的单位面积涂布质量的比值M2满足:M1>M2时,可以使第一电芯的析锂窗口>第二电芯的析锂窗口,可在实现电池组中第二类电芯快速充电时,第一类电芯不易发生析锂等安全问题。
图7是示出使用本申请实施方式的通过电压来控制对电池组中的第一类电芯(以磷酸铁锂电芯为例)进行的阶梯充电时的充电曲线的示例的示意图。
如图7所示,根据本申请实施方式,在对电池组中的第一类电芯(磷酸铁锂电芯)进行阶梯充电时,利用第二类电芯(例如三元电芯)来控制第一类电芯的充电,由于第二类电芯的SOC-OCV曲线的斜率K2更大,因此阶梯充电时的精度更高,能够更精确地显示第一类电芯当前的SOC值,同时,能够实现电池组在利用阶梯充电时,快速充电更加安全、第一类电芯不易发生析锂问题。
例如,图7中,首先以恒流电流I1对第一类电芯进行充电;在经过第1预定时间之后第二类电芯的OCV电压达到V1时,充电电流突变到I2,并以恒流电流I2继续进行充电;在经过第2预定时间之后第二类电芯的OCV电压达到V2时,充电电流突变到I3,并以恒流电流I3继续进行充电;在经过第3预定时间之后第二类电芯的OCV电压达到V3时,充电电流突变到I4,并以恒流电流I4继续进行充电;在经过第4预定时间之后第二类电芯的OCV电压达到V4时, 充电电流突变到I5,并以恒流电流I5继续进行充电;在经过第5预定时间之后第二类电芯的OCV电压达到V5时,充电电流突变到I6,并以恒流电流I6继续进行充电直到将第一类电芯充满。当第一类电芯充满时,第二类电芯的OCV电压成为截止充电电压V6。
如上所述,当电池组中含有不同化学体系电芯,且第二类电芯的SOC-OCV曲线的斜率K2大于第一类电芯的SOC-OCV曲线的斜率K1时,根据第二类电芯的OCV电压来控制第一类电芯的恒流充电电流,因此阶梯充电时的精度更高,从而能够使利用阶梯充电的快充更加安全可靠,并且能够更精确地显示第一类电芯当前的SOC值。
这里,“SOC”表示荷电状态(State Of Charge),其是指当前电芯的剩余电量与相同条件下额定容量的比值,例如可以为100%、99%、90%、80%、70%、60%、50%、40%、30%、20%、10%、0%。“OCV”表示开路电压(Open Circuit Voltage)。
此外,本申请的发明人还发现:使电解液电导率较大且使负极极片的单位面积涂布质量较小可降低电荷转移阻抗Rct和扩散阻抗Rdiff(例如锂离子嵌入和脱出时在靠近集流体侧的负极活性物质中的固相扩散),从而可提高第一类电芯的锂离子传输动力学特性。
本申请中,电解液电导率测试可以直接选择电导电极实现。通常电导电极为面积A、距离L确定的两个平行电极片,对应电极电导常数K。通过电化学交流阻抗测得电阻R,则电导率ζ=K/R。为保证测试的准确性,电导常数K在测试前还需通过标准溶液标定。平行电极片为光亮铂电极或铂黑电极,需要结合电解液的大致电导率和不同型号电导电极的测试范围选择。通常光亮电极用于测量较小的电导率,而铂黑电极用于测量较大的电导率。由于铂黑电极表面积较大,从而降低电流密度以减少或消除极化;测量低电导率溶液时,铂黑电极对电解质有强烈的吸附作用,出现不稳定的现象,这时宜用光亮铂电极。对于水系电解液的测试,直接添加适量电解液于玻璃管内,其添加量需保证液面没过电导电极的极片;而有机电解液则需在充满高纯氩气的手套箱中测试,或根据需要设计密封容器,在接口位置涂覆真空硅脂或凡士林以达到更好的密封效果,最终完成电池组装。组装完成后,将电导电极的两个接线和电化学工作站相接即可进行下一步测试。作为示例的,可以采用电导率仪雷磁DDSJ-318,在25℃、交流阻抗1kHz条件下,测试电解液的电 阻,计算电解液的电导率σ。
本申请中,负极极片的单位面积涂布质量为本领域公知的含义,指的是单位面积上集流体单侧的负极活性物质层的质量,可采用本领域已知的方法测定。例如,取单面涂布且经冷压后的极片、也可以是从电芯中拆解得到的极片(若是双面涂布的极片,可先擦拭掉其中一面的活性物质层),冲切成面积为S1的小圆片,称取质量,记为m1;然后将上述极片表面的活性物质层用溶剂浸泡,从集流体表面全部剥离,称取集流体的质量,记为m2;最后,将活性物质层的质量(m1-m2)除以活性物质的涂布面积S1(即(m1-m2)/S1),从而可得到极片的单位面积涂布质量。
在本申请的一些实施方式中,所述第一电芯的荷电状态-开路电压(SOC-OCV)曲线至少满足以下条件之一:(1)在5%-95%SOC区间,所述第一电芯的SOC-OCV曲线的斜率k1≤5mV/%SOC;(2)所述第一电芯的SOC-OCV曲线中,至少存在一段跨度不低于10%SOC、斜率k1≤5mV/%SOC的平缓曲线。
在本申请的一些实施方式中,所述第二电芯的荷电状态-开路电压(SOC-OCV)曲线至少满足以下条件之一:(1)在5%-95%SOC的区间,所述第二电芯的SOC-OCV曲线的斜率k2>5mV/%SOC,可选地,k2≥6mV/%SOC,进一步可选地,k2≥9mV/%SOC;(2)所述第二电芯的SOC-OCV曲线中,至少存在一段跨度不低于10%SOC、斜率k2>5mV/%SOC的曲线。
本申请中,SOC-OCV曲线斜率可采用本领域公知的的测试方法进行测试。作为示例的,可以采用如下步骤进行测试:
充电SOC-OCV测试(第一和第二类电芯相同):首先得到对应电芯的标称设计,标称容量C,电压应用区间:V1-V2(下限电压-上限电压);
测试流程(电芯衰减情况确认,容量修正):
1)0.33C放电至V1;
2)静置10min;
3)0.33C充电至V2,恒压充电至电流≤0.05C;
4)静置10min;
5)0.33C放电至V1;(记录本步骤放电容量为C0);
测试流程(SOC-OCV测试):
1)0.33C0放电至V1;
2)静置3h;
3)0.05C0充电至V2;(踩点间隔1S;提取电压和容量数据,以本步骤最后的容量作为Cn);
4)静置10min;
数据处理:
以Cn为100%SOC对应点,得到踩点记录下的每个电压及对应充电累积容量所对应的SOC,绘制充电SOC-OCV曲线;通过此方法分别得到第一电芯SOC-OCV曲线1,和第一电芯SOC-OCV曲线2;
斜率测试:
根据充电SOC-OCV曲线,以(SOC1,V1)和(SOC2,V2)两个点,得到对应SOC1~SOC2的斜率K=(V2-V1)/(SOC2-SOC1)。
在本申请的一些实施方式中,所述第一负极极片的压实密度为PD1,所述第二负极极片的压实密度为PD2,其中,PD1<PD2,且0.5≤PD1≤3,0.5≤PD2≤3,单位为g/cm
3。可选地,1≤PD1≤2,1≤PD2≤2。进一步可选地,1.2≤PD1≤1.7,1.2≤PD2≤1.7。
本申请的发明人通过潜心研究发现:析锂窗口、电荷转移阻抗Rct和扩散阻抗Rdiff还与负极极片的压实密度有关(扩散阻抗Rdiff的影响更大)。压实密度越大,颗粒堆积越紧密,此时电解液浸润效果变差,负极活性物质(例如石墨)之间的迁移路径变小,液相扩散的机会变少;另一方面颗粒之间的堆积缝隙变小,离子扩散通路变窄,从而锂离子的嵌入和脱出变得困难,会导致析锂窗口变小。
本申请中,负极极片压实密度可采用本领域已知的方法进行测试。作为示例性的测试方法如下:取单面涂布且经冷压后的负极极片(若是双面涂布的极片,可先擦拭掉其中一面的负极膜层),冲切成面积为S1的小圆片,称其重量,记为m1;测试负极膜层的厚度,记为H;然后将负极膜层擦拭掉,称量负极集流体的重量,记为m2;负极膜层的压实密度dc=(m1-m2)/S1/H。
在本申请的一些实施方式中,所述第一负极极片的单位面积涂布质量为CW1,所述第二负极极片的单位面积涂布质量为CW2,其中,6.49≤CW1≤17,4.54 ≤CW2≤25.51,单位为:mg/cm
2。可选地,7.79≤CW1≤11.69,6.23≤CW2≤15.19。进一步可选地,9.09≤CW1≤11.04,7.73≤CW2≤12.69。更进一步可选地,CW1<CW2。本申请的发明人通过潜心研究发现:负极极片活性物质层的涂布质量需控制在适当的范围内,一方面可以控制活性物质层的厚度,提高负极活性物质层内部反应均匀性,降低活性物质层极化,提升电芯的功率性能;另一方面,可以保证电芯和模组的能量密度较高,降低每瓦时电芯的制造成本。
本申请中,通过对第一负极极片的单位面积涂布质量和第二负极极片的单位面积涂布质量进行优化设计,从而可实现第一类电芯和第二类电芯中负极极片的锂离子扩散路径及容量特性有效兼容,从而进一步提升电池组的体积能量密度及快充安全性。
在本申请的一些实施方式中,所述第一负极极片的负极活性物质和所述第二负极极片的负极活性物质可以独立的选自人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料、钛酸锂中的一种或几种。
在本申请的一些实施方式中,所述第一电芯的数量N与所述第二电芯的数量M之比为0.1~50,可选地为0.3~30,进一步可选地为0.5~10。
[电池包]
在本申请的一个实施方式中,可以将两个或更多个上述电池组组装成电池包,电池包所含电池组的数量取决于电池包的应用和单个电池组的参数。电池包可以包括电池箱和设置于电池箱中的多个电池组,该电池箱包括上箱体和下箱体,上箱体能够盖在下箱体上并与之良好匹配,形成用于容纳电池组的封闭空间。两个或更多个电池组可以按照所需的方式排布于该电池箱中。本申请中,“电池包”是对于一个或多个电池组(或者由多个电芯直接形成的组合)进一步装配电池管理***、热管理***等各种控制和保护***而制成的。
图4是示出本申请的电池包1的一个示例的示意图。图5是示出图4所示的本申请的电池包1的一个示例的分解图。参照图4和图5,在电池包1中可以包括电池箱和设置于电池箱中的多个电池组4。电池箱包括上箱体2和下箱体3,上箱体2用于盖设下箱体3,并形成用于容纳电池组4的封闭空间。多个电池组4可以按照任意的方式排布于电池箱中。
[用电装置]
在本申请的一个实施方式中,本申请的用电装置包括本申请的电池组、或电池包中的至少一种,所述电池组、或电池包可以用作所述用电装置的电源,也可以用作所述用电装置的能量存储单元。所述用电装置包括但不限于移动数字装置(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能***等。
图6是示出将本申请的电池组用作电源的用电装置的一个示例的示意图。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对高功率和高能量密度的需求,可以采用电池包或电池组。
[制造方法及制造设备]
本申请提出一种电池组的制造方法,包括如下步骤:获取第一类电芯和第二类电芯,所述第一类电芯和第二类电芯为不同的化学体系电芯,所述第一类电芯包括N个第一电芯,所述第二类电芯包括M个第二电芯,N和M为正整数,所述第一电芯包括第一负极极片,所述第二电芯包括第二负极极片,所述第一电芯的电解液电导率(25℃)与所述第一负极极片的单位面积涂布质量的比值记为M1,所述第二电芯的电解液电导率(25℃)与所述第二负极极片的单位面积涂布质量的比值记为M2,其中所述电解液电导率的单位为mS/cm,所述单位面积涂布质量的单位为mg/cm
2,M1和M2满足:M1>M2,且0.08≤M1≤11,0.03≤M2≤4.62;以及将所述第一类电芯和所述第二类电芯至少串联的方式电连接,以形成如上所述的电池组。
本申请提出一种电池组的制造设备,包括:夹臂单元,所述夹臂单元用于获取第一类电芯和第二类电芯,所述第一类电芯和第二类电芯为不同的化学体系电芯,所述第一类电芯包括N个第一电芯,所述第二类电芯包括M个第二电芯,N和M为正整数,所述第一电芯包括第一负极极片,所述第二电芯包括第二负极极片,所述第一电芯的电解液电导率(25℃)与所述第一负极极片的单位面积涂布质量的比值记为M1,所述第二电芯的电解液电导率(25℃)与所述第二负极极片的单位面积涂布质量的比值记为M2,其中所述电解液电导率的单位为mS/cm,所述单位 面积涂布质量的单位为mg/cm
2,M1和M2满足:M1>M2,且0.08≤M1≤11,0.03≤M2≤4.62;组装单元,所述组装单元用于将所述第一类电芯和所述第二类电芯以至少串联的方式电连接,以形成如上所述的电池组;以及控制单元,该控制单元用于控制所述夹臂单元和所述组装单元。
由此,使用本申请的制造方法及制造设备制造的电池组可实现含有不同类型化学体系电芯的电池组的快速充电能力及快充过程中的安全性。
下面,通过具体实施例详细描述本申请的技术方案及其优点。
《电芯制备》
参考GB/T 31484-2015《电动汽车用动力蓄电池循环寿命要求及试验方法》,各实施例和对比例中的电芯的制备方法如下。
1、正极浆料的制备
将正极活性材料与导电炭(导电碳可能不止一种)、粘结剂聚偏二氟乙烯(PVDF)及其它正极添加剂按设计目标(此处比例不固定,可根据需求进行)重量比在适量的N-甲基吡咯烷酮(简写为NMP)溶剂中充分搅拌混合,使其形成均匀的、粘度为5000~30000mPa·s的稳定浆料,浆料静置24小时内,不发生凝胶、分层或者沉降等现象。
2、正极极片的制备
将正极浆料均匀涂覆于正极集流体Al箔上,使得干燥后单位面积膜片的涂布重量达到设定值,并对极片进行冷压达到设计压密,分条备用,得到正极极片。
3、电解液的制备
其中一种典型的电解液制备举例(电解液根据设计需求,溶剂、盐和添加剂均可调整):将等量体积的碳酸乙烯酯溶解在碳酸丙烯酯中,然后将适量的六氟磷酸锂盐均匀溶解在该混合溶剂中备用,根据设计添加电解液添加剂,充分溶解均匀后得到电解液。
4、负极极片的制备
将负极活性材料石墨与导电碳黑、粘结剂聚苯乙烯丁二烯共聚物(SBR)、增稠剂羧甲基纤维素钠(CMC)及负极添加剂等按设计重量比在适量的水溶剂中充分搅拌混合,使其形成均匀的负极稳定浆料;将此浆料均匀涂覆于负极集流体Cu箔 上,使得干燥后单位面积膜片的涂布重量达到设定值,并对极片进行冷压达到设计压密,分条备用。
5、隔离膜
选用PP为主要材料的隔离膜等作为电芯隔离膜。
6、电芯的制备
采用常规的电芯制作工艺,将正极极片、隔离膜和负极极片一起卷绕成裸电芯,然后置入电池壳体中,注入电解液,随之进行化成、密封等工序,最终得到可充电动力电芯。
《电池组的组装》
电池组以串联形式电连接的第一类电芯和第二类电芯,所述第一类电芯和第二类电芯为不同的化学体系电芯,所述第一类电芯包括7个第一电芯,所述第二类电芯包括2个第二电芯,以BAAAAAAAB的方式进行排列组装(其中,A代表第一电芯,B代表第二电芯)。
《电解液电导率的测试方法》
采用电导率仪雷磁DDSJ-318,在25℃、交流阻抗1kHz条件下,测试电解液的电阻,计算电解液的电导率σ。
《负极极片的单位面积涂布质量的测试方法》
取单面涂布且经冷压后的极片,擦拭掉其中一面的活性物质层,冲切成面积为S1的小圆片,称取质量,记为m1;然后将上述极片表面的活性物质层用溶剂浸泡,从集流体表面全部剥离,称取集流体的质量,记为m2;最后,将活性物质层的质量(m1-m2)除以活性物质的涂布面积S1(即(m1-m2)/S1),从而可得到极片的单位面积涂布质量。
《极片压实密度的测试方法》
取单面涂布且经冷压后的负极极片(若是双面涂布的极片,可先擦拭掉其中一面的负极膜层),冲切成面积为S1的小圆片,称其重量,记为M1;测试负极膜层的厚度,记为H;然后将负极膜层擦拭掉,称量负极集流体的重量,记为M2;负极膜层的压实密度dc=(M1-M2)/S1/H。
《SOC-OCV曲线斜率的测试方法》
充电SOC-OCV测试(第一和第二类电芯相同):首先得到对应电芯的标称设 计,标称容量C,电压应用区间:V1-V2(下限电压-上限电压);
测试流程(电芯衰减情况确认,容量修正):
1)0.33C放电至V1;
2)静置10min;
3)0.33C充电至V2,恒压充电至电流≤0.05C;
4)静置10min;
5)0.33C放电至V1;(记录本步骤放电容量为C0);
测试流程(SOC-OCV测试):
1)0.33C0放电至V1;
2)静置3h;
3)0.05C0充电至V2;(踩点间隔1S;提取电压和容量数据,以本步骤最后的容量作为Cn);
4)静置10min;
数据处理:
以Cn为100%SOC对应点,得到踩点记录下的每个电压及对应充电累积容量所对应的SOC,绘制充电SOC-OCV曲线;通过此方法分别得到第一电芯SOC-OCV曲线1,和第一电芯SOC-OCV曲线2;
斜率测试:
根据充电SOC-OCV曲线,以(SOC1,V1)和(SOC2,V2)两个点,得到对应SOC1~SOC2的斜率K=(V2-V1)/(SOC2-SOC1);
《快充安全性能的测试方法》
三电极制作:参考标准制作,基于单层叠片制作工艺加入一个镀锂电极作为参比电极;
析锂窗口测试:以第二类电芯体系的三电极测试,得到对应的析锂窗口,具体测试流程如下:
读取第二类电芯基本信息:标称容量C;
电压应用区间:V1-V2(下限电压-上限电压)。
一个典型的测试电流选取原则:X>3C,每间隔1C取一个点测试;1C≤X≤3C,每间隔0.5C取一个点测试;X<1C,每间隔0.2C取一个点。
硬壳验证对比:根据测试得到的析锂窗口,制定如上充电策略,将第一类和第二类电芯在25℃按照上述充电策略,充放电10次,满充状态拆解电池组中第一类电芯及第二类电芯,对比阳极的析锂情况。
《析锂等级判定说明》
析锂等级I:不析锂,拆解满充态阳极表面完全无白色析锂区域,总析锂面积占比<0.1%;
析锂等级II:轻微析锂,拆解满充态阳极表面有白色点状析锂,或少量条状析锂区域,总析锂面积占比0.1%~0.5%;
析锂等级III:中度析锂,拆解满充态阳极表面有白色点状析锂,条状析锂区域,或块状及片状析锂,总析锂面积占比0.5~5%;
析锂等级IV:严重析锂,拆解满充态阳极表面有白色点状,条状析,或块状及片状析锂,总析锂面积占比≥5%;
其中,析锂程度I和II为合格(由于硬壳卷绕设计需考虑电芯特殊位置及制成工艺波动导致的轻微析锂),III及IV等级认为快充不合格。
通过上述《电芯制备》方法,可得到以下的实施例1~13的电池组和比较例1、2的电池组。其中,实施例1~13和比较例1、2中,第一类电芯均采用磷酸铁锂体系电芯(LFP),第二类电芯均采用镍钴锰酸锂523体系电芯(NCM523)。在实施例1~11中,第二类电芯的充放电区间为2.8~4.35V;实施例12中,第二类电芯的充放电区间为2.8~4.4V;实施例13中,第二类电芯的充放电区间为2.8~3.8V。
此外,通过上述的测试方法,可以得到示出实施例1~13与比较例1、2之间的比较结果如表1~3所示。
特别说明,由于体系设计、具体活性物质材料、电解液种类特征添加剂、电芯壳体大小等差异,可能测试得到具体数值有差异,但整理趋势规律应大体符合如下所列结果表1~3。
从表1可知,实施例1~5的电池组中,包括以串联形式电连接的第一类电芯和第二类电芯,第一类电芯和第二类电芯为不同的化学体系电芯,第一电芯包括第一负极极片,第二电芯包括第二负极极片,第一电芯的电解液电导率(25℃)与第一负极极片的单位面积涂布质量的比值记为M1,第二电芯的电解液电导率(25℃) 与第二负极极片的单位面积涂布质量的比值记为M2,其中电解液电导率的单位为mS/cm,单位面积涂布质量的单位为mg/cm
2,M1和M2满足:M1>M2,且0.08≤M1≤11,0.03≤M2≤4.62。本申请发明人发现:电解液电导率与析锂窗口正相关,负极极片的单位面积涂布质量与析锂窗口负相关,电解液电导率与负极极片的单位面积涂布质量的比值M越大,则析锂窗口越大。通过实施例1~5及对比例1~2可以看出:由于第一类电芯和第二类电芯至少以串联连接,当第一电芯的M1、和第二电芯的M2满足:M1>M2时,可以使得第一电芯的析锂窗口大于第二电芯的析锂窗口,可在实现电池组中第二类电芯快速充电时,第一类电芯不易发生析锂等安全问题。
从表2可知,实施例3、6~9的电池组中,第一电芯与第二电芯在满足:M1>M2,且0.08≤M1≤11,0.03≤M2≤4.62的基础上,第一负极极片的压实密度PD1与第二负极极片的压实密度为PD2还满足:PD1<PD2,且0.5≤PD1≤3,0.5≤PD2≤3(单位为g/cm
3)时,第一电芯与第二电芯的负极极片中的活性物质颗粒堆积较为紧密且保有一定的离子扩散路径,可以在保证电池组体积能量密度较高的同时,第一电芯及第二电芯各自的析锂窗口较大,可有效降低快充过程的析锂风险。
从表3可知,实施例3、10、11的电池组中,第一电芯与第二电芯在满足:M1>M2,且0.08≤M1≤11,0.03≤M2≤4.62的基础上,第一负极极片的单位面积涂布质量CW1、第二负极极片的单位面积涂布质量CW2还满足:6.49≤CW1≤17,4.54≤CW2≤25.51(单位:mg/cm
2)时,一方面可以控制第一电芯及第二电芯中负极活性物质层的厚度,提高负极活性物质层内部反应均匀性,降低活性物质层极化,提升第一电芯及第二电芯各自的动力学性能;另一方面,可以保证电芯和模组的能量密度较高,降低每瓦时电芯的制造成本。
从表4可知,实施例3、12、13的电池组中,第一电芯与第二电芯在满足:M1>M2,且0.08≤M1≤11,0.03≤M2≤4.62的基础上,第二电芯的荷电状态-开路电压(SOC-OCV)曲线还满足k2≥6mV/%SOC时,可以进一步优化电池组在快速充电过程中的安全性能,使得第一类电芯不易发生析锂等安全问题。
本说明书中各实施例或实施方式采用递进的方式描述,每个实施例重点说明的都是与其他实施例的不同之处,各个实施例之间相同相似部分相互参见即可。
在本说明书的描述中,参考术语“一个实施方式”、“一些实施方式”、“示意性实施方式”、“示例”、“具体示例”、或“一些示例”等的描述意指结合实施方式或示例描述的具体特征、结构、材料或者特点包含于本申请的 至少一个实施方式或示例中。在本说明书中,对上述术语的示意性表述不一定指的是相同的实施方式或示例。而且,描述的具体特征、结构、材料或者特点可以在任何的一个或多个实施方式或示例中以合适的方式结合。
最后应说明的是:以上各实施例仅用以说明本申请的技术方案,而非对其限制;尽管参照前述各实施例对本申请进行了详细的说明,本领域的普通技术人员应当理解:其依然可以对前述各实施例所记载的技术方案进行修改,或者对其中部分或者全部技术特征进行等同替换;而这些修改或者替换,并不使相应技术方案的本质脱离本申请各实施例技术方案的范围。
Claims (12)
- 一种电池组,所述电池组包括至少以串联形式电连接的第一类电芯和第二类电芯,所述第一类电芯和第二类电芯为不同的化学体系电芯,所述第一类电芯包括N个第一电芯,所述第二类电芯包括M个第二电芯,N和M为正整数;所述第一电芯包括第一负极极片,所述第二电芯包括第二负极极片,所述第一电芯的电解液电导率(25℃)与所述第一负极极片的单位面积涂布质量的比值记为M1,所述第二电芯的电解液电导率(25℃)与所述第二负极极片的单位面积涂布质量的比值记为M2,其中所述电解液电导率的单位为mS/cm,所述单位面积涂布质量的单位为mg/cm 2,M1和M2满足:M1>M2,且0.08≤M1≤11,0.03≤M2≤4.62。
- 如权利要求1所述的电池组,其中,0.33≤M1≤6.42,0.17≤M2≤2.57;可选地,0.63≤M1≤1.94,0.63≤M2≤1.1。
- 如权利要求1或2所述的电池组,其中,所述第一电芯的荷电状态-开路电压(SOC-OCV)曲线至少满足以下条件之一:(1)在5%-95%SOC区间,所述第一电芯的SOC-OCV曲线的斜率k1≤5mV/%SOC;(2)所述第一电芯的SOC-OCV曲线中,至少存在一段跨度不低于10%SOC、斜率k1≤5mV/%SOC的平缓曲线。
- 如权利要求1-3任一项所述的电池组,其中,所述第二电芯的荷电状态-开路电压(SOC-OCV)曲线至少满足以下条件之一:(1)在5%-95%SOC的区间,所述第二电芯的SOC-OCV曲线的斜率k2>5mV/%SOC,可选地,k2≥6mV/%SOC,进一步可选地,k2≥9mV/%SOC;(2)所述第二电芯的SOC-OCV曲线中,至少存在一段跨度不低于10%SOC、斜率k2>5mV/%SOC的曲线。
- 如权利要求1-4任一项所述的电池组,其特征在于,所述第一负极极片的压实密度为PD1,所述第二负极极片的压实密度为PD2,其中,PD1 <PD2,且0.5≤PD1≤3,0.5≤PD2≤3,单位为g/cm 3;可选地,1≤PD1≤2,1≤PD2≤2;进一步可选地,1.2≤PD1≤1.7,1.2≤PD2≤1.7。
- 如权利要求1-5任一项所述的电池组,其中,所述第一负极极片的单位面积涂布质量为CW1,所述第二负极极片的单位面积涂布质量为CW2,其中,6.49≤CW1≤17,4.54≤CW2≤25.51,单位为:mg/cm 2;可选地,7.79≤CW1≤11.69,6.23≤CW2≤15.19;进一步可选地,9.09≤CW1≤11.04,7.73≤CW2≤12.69;更进一步可选地,CW1<CW2。
- 如权利要求1-6任一项所述的电池组,其中,所述第一负极极片的负极活性物质和所述第二负极极片的负极活性物质可以独立的选自人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料、钛酸锂中的一种或几种。
- 如权利要求1-7所述的电池组,其中,所述第一电芯的数量N与所述第二电芯的数量M之比为0.1~50,可选地为0.3~30,进一步可选地为,0.5~10。
- 一种电池包,其中,包括权利要求1-8任一项所述的电池组。
- 一种用电装置,其中,包括权利要求1-8中任一项所述的电池组或者包括权利要求9所述的电池包,且所述电池组或者所述电池包可以作为所述电学装置的电源或者能量存储单元。
- 一种电池组的制造方法,其中,包括如下步骤:获取第一类电芯和第二类电芯,所述第一类电芯和第二类电芯为不同的化学体系电芯,所述第一类电芯包括N个第一电芯,所述第二类电芯包括M个第二电芯,N和M为正整数,所述第一电芯包括第一负极极片,所述第二电芯包括第二负极极片,所述第一电芯的电解液电导率(25℃)与所述第一负极极片的单位面积涂布质量的比值记为M1,所述第二电芯的电解液电导率(25℃)与所述第二负极极片的单位面积涂布质量的比值记为M2,其中所述电解液电导率 的单位为mS/cm,所述单位面积涂布质量的单位为mg/cm 2,M1和M2满足:M1>M2,且0.08≤M1≤11,0.03≤M2≤4.62;以及将所述第一类电芯和所述第二类电芯至少串联的方式电连接,以形成权利要求1-8中任一项所述的电池组。
- 一种电池组的制造设备,其中,包括:夹臂单元,所述夹臂单元用于获取第一类电芯和第二类电芯所述第一类电芯和第二类电芯为不同的化学体系电芯,所述第一类电芯包括N个第一电芯,所述第二类电芯包括M个第二电芯,N和M为正整数,所述第一电芯包括第一负极极片,所述第二电芯包括第二负极极片,所述第一电芯的电解液电导率(25℃)与所述第一负极极片的单位面积涂布质量的比值记为M1,所述第二电芯的电解液电导率(25℃)与所述第二负极极片的单位面积涂布质量的比值记为M2,其中所述电解液电导率的单位为mS/cm,所述单位面积涂布质量的单位为mg/cm 2,M1和M2满足:M1>M2,且0.08≤M1≤11,0.03≤M2≤4.62;组装单元,所述组装单元用于将所述第一类电芯和所述第二类电芯至少串联的方式电连接,以形成权利要求1-8中任一项所述的电池组;以及控制单元,该控制单元用于控制所述夹臂单元和所述组装单元。
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